Rapid Continuous 3D Printing via Orthogonal Dual-Color Photoinitiation and Photoinhibition.

Stereolithographic additive manufacturing technology has developed from point-by-point scanning exposure to layer-by-layer masking curing and even volumetric printing. Rapid prototyping is one of the important goals pursued by researchers. A continuous three-dimensional (3D) printing system based on the dual-color photoinitiation and photoinhibition is proposed with the aim of further improving printing speed. The process of continuous 3D printing is realized through the anti-polymerization layer between the cured part and the window generated by the ultraviolet (UV) light sheet (355 nm), and dynamic masking with the blue light (470 nm). The volume of the anti-polymerization layer can be adjusted by the intensity ratio of the incident lights (IUV, 0/Iblue,0) and the size of UV laser spot to enhance the reflow filling rate of the liquid resin. For the orthogonal Gaussian anti-polymerization layer, an intensity ratio of 28.6 allows for an inhibition volume of 97.1% of the desired rectangular anti-polymerization zone with a height of 1 mm. The simulation analysis of continuous 3D printing process by flow-structure interaction reveals that the increase of the thickness of the anti-polymerization layer effectively improves the filling rate of the resin and the cross-sectional area of printing, and reduces the stress of the cured part. The experiments with two different 3D structures printing demonstrate that the filling rate and the stress have virtually no effect on the printing process at a large-scale thickness of the anti-polymerization layer, and the printing speed is capable of reaching 200 µm/s. Certainly, the printing volume and complexity can be further improved with the improvement of the system and the optimization of the resin.

Multi-wavelength confocal displacement sensing using a highly dispersive flat-field concave grating.

A multi-wavelength confocal displacement sensor based on a flat-field concave grating (FFCG) was proposed and designed; the large dispersion and small volume of the FFCG make it an ideal candidate for replacing the complex dispersive lens group. The designed displacement sensor was calibrated by displacement meter, and the characteristics were measured. Consequently, for the proposed displacement sensor, the displacement range of 6.8 mm was measured with the R-square linearity evaluation coefficient of 0.998, and the sensitivity preceded 17.1 nm/mm. The resolution of the displacement sensor was characterized by 70 µm, as well as a full width at half maximum (FWHM) fluctuating around 1.63 nm, indicating high precision and accuracy in displacement measurement. Moreover, the stability and reliability of the sensor were verified within 20 min, with no significant wavelength shifts, and gentle power fluctuations of 557.73 counts at 520 nm and 563.67 counts at 545.05 nm, respectively.